Imagine: a time-share for rock stars. At the new Setai Resort & Residences on South Beach, Lenny Kravitz is laying down tracks in his recording studio on the seventh floor. Sheryl Crow and her cycling sweetheart Lance Armstrong are sunning next to the infinity pool. Down at the spa, Janet Jackson's bathrobe malfunction is causing a ruckus. This is definitely not your grandmother's time-share on Myrtle Beach.

The Setai, a landmark Art Deco property with an adjacent 40-story tower managed by Amanresorts founder Adrian Zecha, has been transformed into a combination condo-hotel. It's one of the biggest trends in the travel business. When unoccupied, 50 tower residences (which went for $1 million to $12 million and were decorated by Jean-Michel Gathy, who created the looks for Amanwana and Aman-i-Khas) will be turned over to management for its high-end rental pool. Beyond that, private club membership will provide VIP access to Aman properties worldwide. It's no wonder that every apartment in this Modernist Miami-meets-Shanghai palace was sold out to celebrities (and mere millionaires) before the doors even opened last December.

Back in the sixties, when some genius first decided to sell blocks of time rather than bricks and mortar, fractional vacation ownership had some cheesy undertones, with promotional bus trips and sales pitches involving Ginsu knife sets and steam-tray buffets. Lately, however, the concept has morphed into a broader spectrum, with condo hotels, resort residences, fractional real estate properties, and vacation-ownership clubs—all of which evoke a very different image. And in a mind-boggling process of segmentation, new variations on the theme are cropping up everywhere from Palm Beach to Palo Alto to Telluride.

Even before breaking ground, the MGM Grand sold all 576 furnished apartments (with price tags of up to $1.5 million) in the first of three projected condo-hotel towers on its 116-acre Las Vegas campus. Gated-community developers are partnering with Four Seasons and Ritz-Carlton on projects in resort destinations. By 2006, Canyon Ranch and Miraval will expand their wellness empires with holistic-living communities in Miami Beach and Maui, respectively. Ian Schrager is getting in on the act at his latest New York hotel, the Gramercy Park, with a connected residential component of 23 apartments designed by London-based architect John Pawson. And AOL cofounder Steve Case has just acquired a majority stake in Exclusive Resorts, a members-only vacation-home company.

So what's the appeal? For a start, baby boomers are thinking about retirement homes, while boomers' children are looking for their second homes. Neither age group appears to have enough time or interest to manage real estate. When you factor the use you might get out of a weekend residence against the aggravations of ownership, it's easy to see why some people favor this kind of part-time tenure. Setai developer Jonathan Breene explains: "Having the fridge stocked in advance or clothes cleaned and stored by someone else is incredibly alluring for overscheduled individuals. Today, people want everything done for them." Services have reached a new level, from private chefs to 24-hour butlers. Concierges can also arrange jet or yacht charters and snag elusive restaurant reservations.

Then there's the social dynamic. Having weathered parody and counter-culture disparagement, the notion of a country-club community still endures. Deep down in his DNA, Homo sapiens likes to cluster, especially while improving a golf handicap or tasting wine. But these new clubs don't require an Ivy League degree and an ancestor who was on the Mayflower for membership; a hefty down payment is the only requirement. Auberge Resorts—whose Esperanza project in Los Cabos, Mexico, is nearly sold out—also has Calistoga Ranch, a fractional real estate club in Napa Valley consisting of 27 lodges. Buyers pay $710,000 to become equity owners and rub shoulders with noteworthy local winemakers. "Napa is a place where you can take your foot off the pedal," says Mark Harmon, Auberge's president. "The only thing you have to worry about is when you can get back here again."

Anyone who has recently suffered a comprehensive pat down by a TSA agent at the airport knows that the definitions of ordinary travel have changed dramatically in these post-9/11 times. This is being employed as a subtle sales pitch by off-the-beaten-path developers. Peter Forsch, responsible for the Little Nell in Aspen and the Four Seasons Jackson Hole, is currently promoting Spanish Peaks, a 3,500-acre private club-second home community in Montana, with fly-fishing streams, championship golf, and its own high-speed lifts to Big Sky slopes. "When 9/11 happened, we had an uptick of buyers from urban areas," Forsch says, "because this is a safe haven. Let's put it this way: there's no Al Qaeda in Montana." A pristine wilderness setting with high-speed Internet access and other luxury trimmings also happens to have great appeal for those who don't care to jostle for a pool cabana at 1,000-room resorts and who want to know who their neighbors are.

Another key to the burgeoning of the mixed-use sector is a phenomenon known as "togethering," a term coined to describe multihousehold travel, whether it involves a family gathering or a getaway with close buddies. Even top hotels can lack satisfactory accommodations for travelers who demand additional space for nannies and rambunctious teens, heightened privacy, or other special services.

Given a choice between cramming a clan into several suites or spreading out in a multiple-bedroom villa with a private pool and the same amenities available to hotel guests, there are those who can rationalize forking over big money for the sake of more memorable reunions. At least, that's what Brent and Brad Handler were hoping when they established Exclusive Resorts in 2002. "My brother and I traveled together often with our families," Brent says, "but we started to recognize the frustration of doing so as our children grew up and everyone needed more space." The result is a real estate club designed to eliminate both the burdens of owning additional properties and the uncertainties of villa rental. "Renting a villa is like borrowing somebody's car," Brent remarks. "You never know what you're going to find in the glove compartment."

Club membership is also calculated to make high-end real estate more accessible, much as mortgages once made home ownership affordable to a larger segment of the public. Admission to Exclusive Resorts includes a one-time fee of $375,000 (80 percent refundable upon resignation) plus annual dues starting at $15,000. Unless you're good at deconstructing amortization tables or adding up all those à la carte services on a presidential suite, that sounds like a huge payout for 30 days of vacation a year. But Exclusive provides access to houses with an average value of $2.5 million, and 20 percent down on a $2.5 million property is quite a bit higher than the club's membership fee.

Of course, it's hard not to wonder who has that much free time. Think athletes. Former Denver Broncos wide receiver Ed McCaffrey was hired to pitch Exclusive Resorts to celebrity sports pals. To make the deal sweeter, Exclusive Resorts has an alliance with the fractional private plane company NetJets, plus an on-site concierge team. The company's main draw is its collection of 145 houses in 30 destinations, including Hawaii, Paris, Telluride, and Scottsdale. (Don't forget that the opportunity to trade places was what originally made time-sharing so attractive.)

"Choice is a powerful component of our success," Brent points out. "How many homes can people own? How often can they actually return to one resort and be happy with the product?" And now that Steve Case has signed on as chairman, the company is stepping up its acquisitions. Exclusive Resorts and its competitors, such as Abercrombie & Kent Destination Clubs, are elegant solutions for anyone who isn't shopping for another beachfront villa on St. Bart's. However, there's always a traveler who just wants bragging rights at five-star hotels; that's why Leading Hotels has launched a deeded interest vacation-club alliance designed for people who want to live large at Gleneagles or Hôtel de Crillon. Of course, extended residence in hotels is not novel. Oscar Wilde did it. Ditto for Howard Hughes. Pierre Bergé recently put his apartment in the Pierre on the market. And soon Eloise may be able to buy hers in the Plaza: condo developer Elad Properties recently purchased the venerable Fifth Avenue hotel.

From a developer's point of view, the economics of mixed-use seem clear. For one thing, the revenue stream is stable. In the months after September 11, hotel occupancy rates plummeted in some markets, while time-share occupancy remained relatively steady. "It's a pre-paid vacation," says Howard Nusbaum, president of the American Resort Development Association. "People own that week and they're going no matter what." It turns out that resorts paired with any type of fractional real estate, condominiums, or single-family vacation homes are proving more lucrative for investors. "With this business model," says Nusbaum, "there's no imbalance of occupancy because residential always fills the golf courses, tennis courts, restaurants." By planting a five-star hotel next to an equally glossy vacation home enclave, developers also ensure a steady influx of qualified customers who might buy into the lifestyle. According to Auberge Resorts' Harmon, "Building a stand-alone hotel is often a long-term commitment; combined with another investment vehicle to increase the return, this makes it easier to get capital up front."

With all the mixed-use projects suddenly vying for your vacation dollars, it's worth pausing to consider whether this trend is the postmillennial equivalent of peddling Florida swampland. Not exactly. However, before you sign on the dotted line, you should know the difference between investing in real estate and sinking a large chunk of cash into a prepaid nonequity club, even one in which membership is transferable and personal knickknacks can be warehoused until your next visit. Getting in before the ground floor is poured usually helps, but how do you pick a property that's likely to appreciate in value? Sometimes gut instinct helps. The Setai sold out thanks to hotelier Adrian Zecha's track record. When looking at a hole in the ground or a scale model, you need either a fertile imagination or familiarity with the quality and level of service before making that leap of faith. It also doesn't hurt if Lenny Kravitz turns out to be your next-door neighbor.

In this type of real estate deal, a room or suite is sold to an individual. The buyer can opt to place the unit in a rental program and receive revenue to offset costs for the balance of the year. All residents have access to hotel services and amenities. The purchase price can vary from several hundred thousand to several million dollars. In some cases, rental programs will warehouse your personal belongings (which are then reinstalled exactly as you left them).

HOT PROPERTIES: A BUYER'S GUIDE

Regent Bal HarbourExpect that signature Regent luxury at this development set to open in 2006 in Florida's posh Bal Harbour. 1-BEDROOMS FROM $1.75 MILLION; 866/690-4700 www.regenthotels.com

Residences at MGM GrandAdjacent to the famous Las Vegas hotel, three towers (the first opens in mid 2006) will have their own concierge. STUDIOS FROM $450,000; 888/891-1688; www.mgmgrandresidences.com

The SetaiThe star of South Beach is already sold out, but its residences can be rented by the night. DOUBLES FROM $900; 305/520-6000; www.thesetai.com

The TidesAn Art Deco South Beach high-rise, with 45 apartments for sale—made famous by hotelier and music legend Chris Blackwell. SUITES FROM $910,000; 305/932-4800 www.thetideshotel.com

Tucker's Point Club This long-awaited Bermuda beachfront project, the first stage of which is already open, will have a condo hotel, a residence club, and wholly owned residences. There's also golf and a lavish spa. 3-BEDROOM VILLAS FROM $370,000; 441/298-6915; www.tuckerspoint.com

Westin Trillium HouseThe 222-suite resort within Ontario's Village at Blue Mountain ski area will have a courtyard with hot tubs. STUDIOS FROM $200,000; 888/696-2583; www.thevillageatblue.com—Stacy Small

Here, a branded resort such as Ritz-Carlton or Four Seasons sells outright ownership of a private property (an apartment, villa, or estate). Ownership includes amenities like room service and housekeeping. The cost can be high, running several million at the top end.

HOT PROPERTIES: A BUYER'S GUIDE

Canyon Ranch Living A planned community in North Miami Beach, with 467 residences and 151 condo suites. FROM $700,000 FOR A 1-BEDROOM APARTMENT; 305/993-0030; www.canyonranchliving.com

The Cliff Own a piece of a classic St. Martin resort: 10 villas at La Samanna are for sale. FROM $5,631,360 FOR A 4-BEDROOM VILLA; 800/237-1236

Fairway Terraces at Manele These lofty townhouses on the Hawaiian island of Lanai offer tropical living at its best. FROM $1.6 MILLION FOR A 2-BEDROOM UNIT; 800/505-2624; www.lanailuxuryhomes.com

Greenbrier Sporting Club A residential community with 500 houses at West Virginia's Greenbrier. FROM $400,000 FOR A HALF-ACRE BUILDING SITE; 888/741-8989; www.thegreenbriersportingclub.com

Kempinski Hotel Bahía Estepona This 148-unit resort has raised the bar for luxury in Andalusia. FROM $406,250 FOR A STUDIO; 34-95/280-9517; www.kempinski.com/estepona

Parkside Apartments At the sleek Berlin development affiliated with the Ritz-Carlton, you'll get butlers and twice-daily maid service. FROM $997,875 FOR A 2-BEDROOM APARTMENT; 49-30/2200-2363; www.beisheim-center.com

St. Regis San Francisco Condos atop the St. Regis hotel, with luxe accoutrements like a personal chef. FROM $1.4 MILLION FOR A 2-BEDROOM APARTMENT; 415/979-9966; www.stregisresidences.com

Spanish Peaks At this new Montana resort, owners have ski-in, ski-out access to Big Sky. FROM $800,000 FOR A 2-BEDROOM CONDO; 877/995-3100 OR 406/995-3100; www.spanish-peaks.com

Time Warner Center Just about every mogul has bought into these two prime Manhattan towers—One Central Park and the Residences at Mandarin Oriental. FROM $3.9 MILLION FOR A 2-BEDROOM APARTMENT; 212/823-9300; www.onecentralpark.com

W Dallas Victory The first of at least five planned residences for the W group—61 downtown apartments. FROM $370,000 FOR A 1-BEDROOM UNIT; 214/777-4300; www.victoryresidences.com—S.S.

This scenario involves buying a block of time—which can range from several weeks to several months—at a complex that's typically run by a hotel company such as Hyatt, Westin, or Marriott. Accommodations range from studios to five-bedroom units. Prices start as low as $20,000 and can top out at $1 million, depending on the location, club, size of unit, and time allotment. Buyers become "deeded owners" of the property, a distinction typically shared with 6 to 12 people.

HOT PROPERTIES: A BUYER'S GUIDE

Calistoga RanchThe new vineyard retreat on 157 acres in the upper Napa Valley features a member-owned lodging club. Each two-bedroom residence has an outdoor living room as its centerpiece. Owners can store up to 1 1/2 cases of wine in a special cave and receive preferential treatment at all Auberge Resorts. FROM $425,000 FOR A 2-BEDROOM LODGE; 800/411-1003; www.calistogaranch.com

Four Seasons Residence Club ScottsdaleSet in the heart of the Sonoran Desert, this residence club features 44 two-bedroom adobe-style villas and 51 private houses on the grounds of the luxe Four Seasons resort and the Troon North golf complex. FROM $23,000 FOR A 2-BEDROOM VILLA; 480/515-5700; www.fourseasons.com

Hotel St-Barth Isle de FranceNow there's a way to get a room on St. Bart's during the high season: the tony seaside resort is selling villas and cottages. Residents can use Isle de France's restaurant, its Molton Brown Spa, and of course that fabulous beach. FROM $250,000 FOR A 1-BEDROOM RESIDENCE; 800/627-6345; www.isle-de-france-residences.com

Pond Bay ClubA sister project to Hotel St-Barth Isle de France, Pond Bay consists of 50 exquisitely furnished three- and four-bedroom cottages and villas on highly desirable beachfront property on the island of St. John in the U.S.V.I. FROM $275,000 FOR A 3-BEDROOM HOUSE; 888/649-3155; www.foliocollection.com

Roaring Fork ClubMembership in Roaring Fork, a development inspired by the great camps of the Adirondacks, is by invite only. Located on the outskirts of Aspen in Basalt, Colorado, it has stylish log-cabin accommodations, great fishing, and a Jack Nicklaus-designed golf course. CALL FOR PRICES; 970/927-9000; www.roaringforkclub.net—S.S.

Abercrombie & Kent Destination ClubsDESCRIPTION High-end tour and safari company A&K partnered with the pioneering Private Retreats club in 2003. The formula was so successful that they formed a second club, Distinctive Retreats. More are plannedTHE COST Fee: $295,000-$495,000, refundable. Annual dues: $9,500-$13,500PORTFOLIO 135 residences in 36 destinations, from Los Cabos to Bermuda to TuscanyPROS AND CONS No restrictions on length of stay. Nightly fee ($175-$195)CONTACT 800/925-7577; www.akdestinations.com

Portofino ClubDESCRIPTION The newest in an increasingly crowded field, Portofino Club has Brian Windle, the former Starwood executive credited with branding W Hotels, leading its marketingTHE COST Fee: from $250,000, 80 percent refundable. Annual dues: from $15,000 PORTFOLIO 23 residences in 17 destinations, from the Portofino Coast of Italy to Vail, ColoradoPROS AND CONS Gourmet kitchens with all the newest dinnerware. Usage limited to 42 nights a yearCONTACT 866/659-9990; www.theportofinoclub.com

Leading Residences by Leading Hotels of the WorldDESCRIPTION With a wide range of properties around the world to draw from, Leading Residences—from the Leading Hotels of the World group—could quickly eclipse competitors when it launches any day nowTHE COST Fee: estimated $325,000PORTFOLIO May include 25 properties, from the Hôtel de Crillon in Paris to Scotland's GleneaglesPROS AND CONS Accommodations in historic hotels. Short- and long-term real estate opportunitiesCONTACT 800/223-6800; www.lhw.com

• The Camelback Inn, a JW Marriott resort in Scottsdale, Arizona, has been a condo hotel since the late 1960's. The Breakers in Palm Beach was one of the first hotels to offer hotel residences—the condos at Breakers Row have been in existence since the early 1980's.

• Gwyneth Paltrow has reportedly bought a property at the Esperanza resort in Los Cabos, Mexico, where she honeymooned with musician Chris Martin.

• Details on hotel and real estate opportunities can be found at www.condohotelcenter.com, a site devoted to the subject.

• Consumer advice is available through the American Resorts Development Association (202/371-6700), an advocacy group for both buyers and developers.